Electrical timing system



Dec. 23, 1947. w. R. AIKEN 2,433,254

ELECTRICAL TIMING SYSTEM Filed Jan. 7, 1946 r 24 r 34 1 (Z2 32 27 E 120/"? 'F M 3; pze 1H I N V EN TOR. M1 1 MM Foss Awe/v Arroe/vixsPatented Dec. 23, 1947 UNITED STATES PATENT OFFIEE 2,433,254 ELECTRICALTIMING SYSTEM William Ross Aiken, Berkeley, Calif.

Application January 7, 1946, Serial No. 639,683

The present invention relates to timing devices adapted to delaycommencement of an initiated operation and to determine the durationthereof, such devices being employed in signalling apparatus, weldingequipment, heating arrangements, and the like.

More particularly, the present invention relates to electrical timingcircuits employing tubes of the kind which become conductive only when acritical minimum voltage is applied thereto, in combination with meansfor building up the required voltage over a predeterminable period oftime.

It is the principal object of the present invention to provide a timingsystem adapted to delay operation of a device controlled thereby andcapable of maintaining the controlled device in operating condition fora predetermined interval of time.

It is another object of the present invention to provide an electrictiming system which is,

tion to so arrange an electric timing system of the type referred tothat weak currents incident to the operation thereof are at no timescon,-

ducted through relay contacts so that failure due to corrosion ofcontacts is impossible.

Other objects of the present invention will appear from a description ofthe accompanying drawing, wherein the single. figure shows a time delaysystem embodying my invention.

' The system of my invention utilizes a plurality of tubes each of whichpossesses two electrodes and is of the type filled with an inert gassuch as neon; it is unable to conduct any appreciable current until asufficient voltage is placed across its electrodes to ionize the gas,whereupon it will conduct current until the applied voltage decreasesbelow a critical value required to keep the gas ionized.

According to my invention systems utilizing tubes of the type describedmay be arranged so as to be capable of controlling not onlycommencement, but also duration of an initiated 2 Claims. (Cl. -320)operation over accurately predetermined periods of time. Additionally,such systems may be made to predetermine the duration of intervalsbetween a series of sequential operations at will. An arrangement ofthis type is illustrated by way of example in the figure, wherein 20 isa battery, 2| a master control switch, 22 a timing resistor, and 25 acondenser, all connected in series. Condenser 25 in turn is connectedacross a gasdischarge tube 23 of the type previously described, and arelay 24. Means are provided in the form of a normallyopen'relay-operated contact 28 shunted across condenser 25 to preventinopportune recharging of said condenser 25 upon closing'of said contact,28. Relay 24 is connectible across battery 20 through a reducingresistor 21, a normally open relay-operated contact 26, and a normallyclosed relay-operated contact 30.

Battery 20 is arranged'to charge a second condenser 35 through a secondtiming resistor 32. Condenser 35 is connected across a second gasdischarge tube 33 and a second relay 34, which latter may be of a muchsimpler form than relay 24. Charging of condenser 35 upon closing ofmaster control switch 2| is initially prevented by a normally closedrelay-operated contact 38 shunted across condenser 35.

When master control switch 2| is closed, condenser 25 is charged frombattery 20 through timing resistor 22 until the voltage stored up incondenser 25 is sufilcient to ionize tube 23 whereupon the dischargecurrent of condenser 25 through tube 23 will operate relay 24 to closeinitially open contact 26, thus connecting relay 24 across battery 20and establishing a desired working status for whatever apparatus may becontrolled by relay 24, relay-operated control switches for suchapparatus being indicated at '40 and 4! in the figure. According to myinven tion, actuation of relay 24 is arranged to also close initiallyopen contact 28 which shunts condenser 25 so that the same is dischargedand cannot be recharged as long as contact 28 remains closed. Inaddition, actuation of relay 24 is arranged to open initially closedcontact 38 so that condenser 35 may now charge from battery 20 throughtiming resistor 32. As soon-as condenser 35-is charged to a voltagesufflcient to ionize tube 33, relay 34 disposed in the circuit of tube33 is excited, in which condition it is arranged to open normally closedcontact 30, thus interrupting the circuit supplying relay 24 withcurrent from battery 20. As a result thereof, relay 24 returns toinoperative position, terminat acaacu ing whatever operation may becontrolled by said relay. In addition, deenergization of relay 24 openscontacts 25 and 28 and closes contact 28 establishing conditions underwhich condenser 25 may recharge while condenser 35 is discharged and isprevented from recharging. As a result thereof, relay 34 is deenergizedand permits return of relay-operated contact to its normal closedposition. Hence initial conditions are established throughout thesystem, permitting condenser 25 to recharge and introducing a new cycleof operation.

The time delay between initiation 01' an operation by closing of mastercontrol switch 2| and actual commencement of an operation as controlledby actuation of relay 24 may be predetermined by selecting proper valuesfor timing resistor 22 and condenser 25, either or both of which may bemade variable. The duration of operation of a device controlled by thesystem of my invention may be predetermined by selecting the propervalues for timing resistor 22 and condenser 35 which may likewise bemade variable to permit adjustment to suit particular requirements. Thetime interval between successive operations of a controlled mechanism isagain determined by the values of resistor 22 and condenser 25. In viewof the simple task to be performed by relay 34 in the system of myinvention as against the diversified control operations of relay 24, itwill be understood that a relay of the simplest and most inexpensiveconstruction may be used as relay 24 so that the cost of a second relayin addition to the more complex main control relay 24 will be verysmall.

In a practical embodiment of my invention according to the figure Iemployed components having the following values:

Voltage of battery 20: 125 volts.

Capacity of condenser 28: 4 microfarads.

Capacity of condenser 38: 4 mierofarads.

Critical voltages of tubes 23 and 35: ionizing voltage, 105 volts;deionizing voltage, 85 volts.

Value of resistor 22: 15 megohms.

Value of resistor 32: 10 megohms.

Value of resistor 21: 15,000 ohms.

Relay 24: 5,500 ohms.

Relay :4: 5,500 ohms.

I claim:

1. An electric timing system including a first and second capacitor,normally disabled means for charging said second capacitor, a first gasdischarge tube and a first relay in series and connected across saidfirst capacitor, a second discharge tube and a second relay in seriesand connected across said second capacitor, a circuit including inseries said first relay, a normally open contact, a normally closedcontact, and a source of voltage, said first relay being adapted, uponexcitation, to close said normally open contact and to render effectivesaid normally disabled means for charging said second capacitor, andsaid second relay being adapted, upon excitation, to open said normallyclosed contact.

2. An electrical timing system having a source of voltage, first andsecond circuits, each including a condenser. and a gas discharge tubeand a relay connected across said condenser; normally effective meansfor charging the condenser of said first circuit from said source ofvoltage, and normally inefiective means for charging the condenser ofsaid second circuit from said source of voltage; and a third circuitincluding said source of voltage, the relay of said first circuit, 2.normally open contact and a normally closed contact, said first relaybeing adapted upon excitation thereof through discharge current fromsaid first condenser to close said normally open contact and to rendereffective said normally disabled means for charging said secondcondenser, while disabling said normally effective means for chargingsaid first condenser, and said second relay being adapted uponexcitation thereof to open said normally closed contact.

WILLIAM ROSS AIKEN.

REFERENCES CITED UNITED STATES PATENTS Name Date Kelly May 16, 1933Number 1,909,471

